Identification of novel inhibitors targeting serine acetyltransferase from Neisseria gonorrhoeae.

is an obligate human pathogen and the etiological agent of the sexually transmitted infection, gonorrhoea. The rapid emergence of extensively antimicrobial-resistant strains, including those resistant to all frontline antibiotics, has led to being labelled a priority pathogen by the World Health Organization, highlighting the need for new antimicrobial treatments. Given its absence in humans, targeting cysteine biosynthesis has been identified as a promising avenue for developing new antimicrobials against bacterial pathogens.

Earth's Climate History Explains Life's Temperature Optima.

Why does the growth of most life forms exhibit a narrow range of optimal temperatures below 40°C? We hypothesize that the recently identified stable range of oceanic temperatures of ~5 to 37°C for more than two billion years of Earth history tightly constrained the evolution of prokaryotic thermal performance curves to optimal temperatures for growth to less than 40°C. We tested whether competitive mechanisms reproduced the observed upper limits of life's temperature optima using simple Lotka-Volterra models of interspecific competition between organisms with different temperature optima. Model results supported our proposition whereby organisms with temperature optima up to 37°C were most competitive.

Evidence for a short-lived resonance state in enzyme catalysis via rate-equation convolution.

At the cellular level, all biological function relies on enzymes to provide catalytic acceleration of essential biochemical processes driving cellular metabolism. The enzyme is presumed to lower the activation energy barrier separating reactants from products, but the precise mechanism remains unresolved. Here we examine the temperature dependence of the enzyme-catalyzed dissociation of p-nitrophenyl-α-D-glucopyranoside (pNPG), a chromogenic analog for maltose, isomaltose, and sucrose disaccharide sugars, into p-nitrophenol (pNP) and glucose (monosaccharide).

Chemical Mapping Exposes the Importance of Active Site Interactions in Governing the Temperature Dependence of Enzyme Turnover.

Uncovering the role of global protein dynamics in enzyme turnover is needed to fully understand enzyme catalysis. Recently, we have demonstrated that the heat capacity of catalysis, Δ , can reveal links between the protein free energy landscape, global protein dynamics, and enzyme turnover, suggesting that subtle changes in molecular interactions at the active site can affect long-range protein dynamics and link to enzyme temperature activity. Here, we use a model promiscuous enzyme (glucose dehydrogenase from ) to chemically map how individual substrate interactions affect the temperature dependence of enzyme activity and the network of motions throughout the protein.

Serine acetyltransferase from Neisseria gonorrhoeae; structural and biochemical basis of inhibition.

Serine acetyltransferase (SAT) catalyzes the first step in the two-step pathway to synthesize l-cysteine in bacteria and plants. SAT synthesizes O-acetylserine from substrates l-serine and acetyl coenzyme A and is a key enzyme for regulating cellular cysteine levels by feedback inhibition of l-cysteine, and its involvement in the cysteine synthase complex. We have performed extensive structural and kinetic characterization of the SAT enzyme from the antibiotic-resistant pathogen Neisseria gonorrhoeae.

The Inflection Point Hypothesis: The Relationship between the Temperature Dependence of Enzyme-Catalyzed Reaction Rates and Microbial Growth Rates.

The temperature dependence of biological rates at different scales (from individual enzymes to isolated organisms to ecosystem processes such as soil respiration and photosynthesis) is the subject of much historical and contemporary research. The precise relationship between the temperature dependence of enzyme rates and those at larger scales is not well understood. We have developed macromolecular rate theory (MMRT) to describe the temperature dependence of biological processes at all scales.

Dynamical origins of heat capacity changes in enzyme-catalysed reactions.

Heat capacity changes are emerging as essential for explaining the temperature dependence of enzyme-catalysed reaction rates. This has important implications for enzyme kinetics, thermoadaptation and evolution, but the physical basis of these heat capacity changes is unknown. Here we show by a combination of experiment and simulation, for two quite distinct enzymes (dimeric ketosteroid isomerase and monomeric alpha-glucosidase), that the activation heat capacity change for the catalysed reaction can be predicted through atomistic molecular dynamics simulations.

A complete thermodynamic analysis of enzyme turnover links the free energy landscape to enzyme catalysis.

Our understanding of how enzymes work is coloured by static structure depictions where the enzyme scaffold is presented as either immobile, or in equilibrium between well-defined static conformations. Proteins, however, exhibit a large degree of motion over a broad range of timescales and magnitudes and this is defined thermodynamically by the enzyme free energy landscape (FEL). The role and importance of enzyme motion is extremely contentious.

On the Temperature Dependence of Enzyme-Catalyzed Rates.

One of the critical variables that determine the rate of any reaction is temperature. For biological systems, the effects of temperature are convoluted with myriad (and often opposing) contributions from enzyme catalysis, protein stability, and temperature-dependent regulation, for example. We have coined the phrase "macromolecular rate theory (MMRT)" to describe the temperature dependence of enzyme-catalyzed rates independent of stability or regulatory processes.

Reconstructed Ancestral Enzymes Impose a Fitness Cost upon Modern Bacteria Despite Exhibiting Favourable Biochemical Properties.

Ancestral sequence reconstruction has been widely used to study historical enzyme evolution, both from biochemical and cellular perspectives. Two properties of reconstructed ancestral proteins/enzymes are commonly reported--high thermostability and high catalytic activity--compared with their contemporaries. Increased protein stability is associated with lower aggregation rates, higher soluble protein abundance and a greater capacity to evolve, and therefore, these proteins could be considered "superior" to their contemporary counterparts.